An important step in the deployment is legitimate

Recently, for the first time since the “opening of the eyes”, JWST has crossed an important new milestone by introducing its guidance system.

Last week, the James Webb Space Telescope, the new favorite of NASA astronomers, officially opened its eyes and captured its first image. This was a very important step as it proved the effectiveness of the optical system, but JSWT is still far from fully operational. But the deadline is now fast approaching with the launch of its “Compass” service.

In fact, for the first time, this Canadian instrument, baptism β€œFine guidance system”(FGS) Stabilize, then lock the telescope to a specific targetWhich demonstrates the ability to focus on a specific object.

It is difficult to overstate the importance of this crucial step; Effective, Without this instrument, JWST would be unable to reach incredible levels of accuracy Necessary for such observations. All future JWST work therefore depends directly on the proper functioning of this machine. The confirmation was, of course, a great relief to the engineers who had devoted so many years of superhuman effort to it.

Essential for a high-tech “compass” installation

Now that FGS is in place, there is no question of giving up on technical unemployment. He will even play a decisive role in the sequence of events. In fact, the first pictures are only expected in a few months. Until then, NASA will keep each subsystem awake one by one to make sure they are working properly. But most of all, we need to complete the installation of the original mirror. And to accomplish this infinitely subtle task, the help of FGS will be invaluable.

Unlike other telescopes like the Hubble, JWST’s main mirror is not made of a single piece; Instead it consists of Eighteen hexagonal subunits Which makes a single mirror 6.5 m in diameter. On the one hand, without this extremely bold method, NASA would never have been able to equip a telescope with such a large mirror, and therefore so powerful. But on the other hand, it is also a Absolutely huge engineering challenge qHe forced the agency to double its seriousness, but also its cunning.


Virtually no margin for error

In fact, in order for the telescope to work as intended, all of these mirrors must be aligned with extraordinary precision. And at this level, there is not the slightest margin for NASA error. Because when it comes to portraits of billions of light-years distant stars, One millimeter of offset already represents an error far greater than the telescope standard.. Summary: Any significant deviation is simply unacceptable.

This exceptional requirement of precision makes the installation phase last so long. In fact, when it landed in space on the Ariane 5 launcher, the fragile telescope suffered massive vibrations, unfortunately inevitable despite NASA warnings.

After this passage in the shaker, so it is more important to be very careful about the position of these hexagons. Otherwise, there will be a deviation, admittedly slight, but inconsistent with the completely identical mirror required by JSWT. Because when he reached space, the various units had to move a bit. This very small difference caused the first optical test to be produced 18 pictures of the same planet; It is an image of the same object that was reflected from each individual mirror with a slight offset. These different points also form a reference element which will help in calibrating the mirrors later.

Since waking up in the middle of space, JWST has been squinting; Its first optical experiment produced 18 images of the same celestial body, one for each individual mirror. At the end of the alignment process they will become one. NASA

The stretch of the house is getting closer

To ensure the accuracy of this calibration, the individual mirrors are mounted on a set of motors that move very slowly to the desired position. There is no question of going too fast and taking the slightest risk of damage, since it is impossible for Hubble to repair JWST in the event of an error. And that’s where FGS comes in. It will serve to define a common point of reference; This will instead allow each mirror to be adjusted to the ideal position.

Once NASA is satisfied with this alignment, the telescope will move closer to home expansion. During this last critical step, he will have to wait until he has all the materials Completely empty all the heat Accumulated during takeoff.

In fact, the telescope has all the equipment Specially designed to work at -233 degrees Celsius. And at this level, for alignment of mirrors, the slightest deviation can create unacceptable inconsistencies; Here again, the slightest mistake can call into question the results of the observation. JWST therefore has to wait wisely until its head is completely cooled.

Then he can go to the very last stage: The final calibration of the instrument, Which is expected around June If all goes as planned, the telescope will start showering us with images for the year ahead. Together, we hope, interesting images and revolutionary discoveries are at risk.

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